1. Field of the Invention
The present invention relates to a method for determining the existence and position of a repeater, and more particularly to a method for determining the existence of a repeater in a mobile communication system using a portable Internet signal and a method for measuring a position of a mobile station using the repeater.
2. Description of the Related Art
Recently, a position measurement technique using a pilot signal of a mobile communication system has been employed in various realms. A mobile communication system measures a predetermined position of a mobile station mainly using a triangulation procedure known as a Time Difference of Arrival (TDOA) scheme which calculated the TDOA of a base station pilot signal.
FIG. 1 is a view for explaining a method for measuring the position of a mobile station using the conventional TDOA scheme wherein the position of the mobile station is measured based on TDOA of signals transmitted to a mobile station from different base stations such as a first base station, a second base station, and a third base station. In other words, propagation TDOA is calculated, which is proportional to a difference between a distance from the first base station to the mobile station and a distance from the third base station to the mobile station based on the second base station, and the mobile station is positioned at a point holding a constant difference between the distance from the first base station to the mobile station and the distance from the third base station to the mobile station. In other words, as shown in FIG. 1, two hyperbolas are obtained from three base stations, and an intersection point of the two hyperbolas becomes the position of the mobile station. In this case, the TDOA is usually measured through a cross correlation scheme.
However, the mobile communication system employs a repeater for amplifying a pilot signal of a base station in order to deliver a signal having stronger intensity to a mobile station because signals of the base station are attenuated according to distances. In particular, the mobile communication system allows the signals of the base station to be delivered through the repeater to locations which cannot receive the signals of the base station, such as downtown buildings or undergrounds (e.g., subways and underground structures, etc.). However, if a repeater is installed, the pilot signal of the base station is delivered to the mobile station through the repeater. Therefore, the pilot signal is delayed by the time to correspond to the distance passing through the repeater (e.g., several kilometers to several tens of kilometers) when the pilot signal of the base station is passed through the repeater rather than the pilot signal of the base station is not passed through the repeater
In addition, the delay of the pilot signal of the base station due to the repeater induces an error in the measurement of a distance between the base station and the mobile station. Accordingly, when the position of the mobile station is measured through the TDOA scheme, the delay due to the repeater must be considered by determining if the received pilot signal of the base station is delivered through the repeater.
Conventionally, a chip delay of the received base station pilot signal is determined, and, if the chip delay has a large value, it is determined that the received base station pilot signal was transmitted from a repeater. However, through this chip delay determining method, it is difficult to accurately determine if the received base station pilot signal was transmitted from repeater and whether a reference base station signal if the reference base station signal was transmitted from the repeater. In addition, when it is difficult to determine the existence of the repeater, it is impossible to measure the position of a mobile station using the base station pilot signal.
Accordingly, it is necessary to develop a technique for determining the existence and location of a repeater.
Recently, a portable Internet system has been developed in such a manner that the portable Internet system has a superior signal receiving rate even in environments such as an urban downtown, an RF shadow area, and an indoor area, does not require a repeater, and can interwork with the mobile communication system. Accordingly, it is possible to more exactly determine the existence of a repeater and measure the position of a mobile station using the portable Internet system.